1. Field of the Invention
The present invention relates to a platinum complex compound useful as a light-emitting material, and an organic electroluminescence device (hereinafter also referred to as “an organic EL device) using the same.
2. Description of the Related Art
Organic electroluminescent devices are capable of obtaining emission of high luminance by low voltage driving, and actively researched and developed in recent years. An organic EL device generally consists of a pair of electrodes with an organic compound layer including a light-emitting layer, and electrons injected from the cathode and holes injected from the anode are recombined in the light-emitting layer, and generated energy of exciton is used for emission.
The increase in efficiency of the devices has been advanced by the use of phosphorescent materials. Iridium complexes and platinum complexes are known as the phosphorescent materials, and a platinum complex light emitting material capable of light emission of blue to green is reported (e.g., JP-A-2007-19462 (The term “JP-A” as used herein refers to an “unexamined published Japanese patent application”.)). The light-emitting layer of an organic electroluminescence device using emission of phosphorescence is formed by the addition of a phosphorescent material to the material bearing charge transportation (a host material).
The improvement of luminance of light emission of an organic electroluminescence device is desired. As a method for improving luminance of light emission of an organic electroluminescence device, a method of increasing addition concentration of the phosphorescent material in a light emitting layer is known. However, by the increase in the addition concentration of a phosphorescent material, light emission of the organic electroluminescence device widens to the long wavelength region, as a result there arises a problem that chromaticity change of light emission becomes large by the addition concentration of the phosphorescent material. Therefore, such a phosphorescent material that chromaticity of emission does not depend upon the addition concentration of the phosphorescent material is desired.